import java.util.Stack;
 ////用栈实现队列
public class MyQueue {
    private Stack<Integer> s1;
    private Stack<Integer> s2;

    public MyQueue(Stack<Integer> s1, Stack<Integer> s2) {
        this.s1 = s1;
        this.s2 = s2;
    }

    public void push(int x){
        s1.push(x);
    }
    public int pop(){
        if (empty()){
            return -1;
        }
        if (s2.empty()){
            while (!s1.empty()){
                s2.push(s1.pop());
            }
        }
        return s2.pop();
    }
    public int peek(){
        if (empty()){
            return -1;
        }
        if (s2.empty()){
            while (!s1.empty()){
                s2.push(s1.pop());
            }
        }
        return s2.peek();
    }
    public boolean empty(){
        return s1.empty() && s2.empty();
    }
}
